From 78505d2a8b7db9fc5e8b9fd67d2a79223c0596c1 Mon Sep 17 00:00:00 2001
From: hikerstk <hikerstk@178a84e3-b1eb-0310-8ba1-8eac791a3b58>
Date: Thu, 24 Nov 2011 10:20:12 +0000
Subject: [PATCH] Added lost improvement: make sure that both wheels of an axis
 are touching the ground if at least one wheel touches it (if only one wheel
 touches the ground, the kart will get a strong angular impulse and turn
 rapidly).

git-svn-id: svn+ssh://svn.code.sf.net/p/supertuxkart/code/main/branches/physics@10251 178a84e3-b1eb-0310-8ba1-8eac791a3b58
---
 src/physics/btKart.cpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/physics/btKart.cpp b/src/physics/btKart.cpp
index e53c7bb6d..2266d2d99 100644
--- a/src/physics/btKart.cpp
+++ b/src/physics/btKart.cpp
@@ -326,6 +326,30 @@ void btKart::updateVehicle( btScalar step )
         if(m_wheelInfo[i].m_raycastInfo.m_isInContact)
             m_num_wheels_on_ground++;
 	}
+    // Work around: make sure that either both wheels on one axis
+    // are on ground, or none of them. This avoids the problem of
+    // the kart suddenly getting additional angular velocity because
+    // e.g. only one rear wheel is on the ground.
+    for(i=0; i<m_wheelInfo.size(); i+=2)
+    {
+        if( m_wheelInfo[i  ].m_raycastInfo.m_isInContact != 
+            m_wheelInfo[i+1].m_raycastInfo.m_isInContact)
+        {
+            int wheel_air_index = i;
+            int wheel_ground_index = i+1;
+            
+            if (m_wheelInfo[i].m_raycastInfo.m_isInContact)
+            {
+                wheel_air_index = i+1;
+                wheel_ground_index = i;
+            }
+
+            btWheelInfo& wheel_air = m_wheelInfo[wheel_air_index];
+            btWheelInfo& wheel_ground = m_wheelInfo[wheel_ground_index];
+
+            wheel_air.m_raycastInfo = wheel_ground.m_raycastInfo;
+        }
+    }   // for i=0; i<m_wheelInfo.size(); i+=2
 
 	updateSuspension(step);